At the weekly Neonatal Unit Multidisciplinary Team Meeting the Microbiologist was asked about a baby with Cytomegalovirus infection. The baby had been born at term but was very small, below the 3rd centile. Other than the size of the baby there were no other concerns during the pregnancy. The baby had looked otherwise well and was behaving normally. A number of tests had been done to look for a reason why the baby might be small and a urine sample had tested positive for Cytomegalovirus DNA by PCR.
 
The Neonatologists wanted to know what they should do next and the MDT members looked at the Microbiologist expectantly, who started to feel somewhat uncomfortable under all those stares…

​What is Cytomegalovirus?
Cytomegalovirus (CMV) is a Human Herpes Virus (HHV); in fact it is HHV5 or the fifth HHV discovered. It is a double-stranded DNA virus. Like the other HHV (Herpes Simplex Virus 1 & 2 (cold sores and genital herpes), Varicella Zoster Virus, Epstein-Barr Virus, HHV6, HHV7 and Kaposi Sarcoma Virus) CMV causes a latent infection with virus persisting in body tissues from where it can reactivate if the patient’s immune system becomes compromised.
 
CMV is often described as a “kissing contacts” infection in that close personal contact is usually required to spread the infection, usually via droplets from the upper respiratory tract… hence the risk of catching CMV when kissing someone with CMV! In the UK it is estimated that 60-80% of the population has been infected with CMV by the age of 18 years.
 
Congenital infection is one that occurs due to exposure to the infecting microorganism in utero i.e. before birth. In order for the foetus to become infected the virus has to cross the placenta and the risk of this occurring differs at different stages of pregnancy. With primary maternal infection (not reactivation of latent infection) the rates of transfer are:

• First trimester – 37%
• Second trimester – 40%
• Third trimester – 65%

 
If you already have CMV you will not necessarily reactivate it in pregnancy and it is not known how many reactivations actually occur in pregnancy. The risk of infection following reactivation is very low, around 0.15-2%, as maternal antibody provides protection to the baby as well as the mother. However acquiring CMV (primary CMV) in pregnancy carries the highest risk of congenital CMV; but remember most women have already had CMV before they become pregnant and so the overall risk to the foetus is low.
 
How does congenital CMV present?
It is estimated that the rate of congenital CMV is around 0.6% live births in developed countries, but most of these infections are not diagnosed because 90% of the babies are asymptomatic at birth. The symptoms and signs of possible CMV that might be present at birth include:

• Petechiae (bruising)*
• Early jaundice <2 days (all babies become jaundiced to some degree but from day 2 to day 7 as they breakdown foetal haemoglobin and produce adult haemoglobin)
• Hepatosplenomegaly*
• Intra-uterine growth retardation (IUGR)  
• Thrombocytopenia (low platelet count)*
• Microcephaly (small head)*
• Intracranial calcifications (calcified brain tissue seen on ultrasound)
• Polymicrogyria and ventriculomegaly (brain abnormalities)*
• Sensorineural hearing loss (unilateral or bilateral)
• Chorioretinitis (inflammation in the eye)
• Seizures*

* Indicators of possible life-threatening infection

​How is congenital CMV diagnosed?
If a mother is diagnosed with CMV in pregnancy it is normal practice to offer amniocentesis to see if the foetus has also been infected. If CMV DNA is detected by PCR in amniotic fluid then the foetus has been infected because the only way for CMV to get into the amniotic fluid is for the foetus to pee it out into the amniotic sack. Amniocentesis to look for CMV can only be relied upon 6-8 weeks after maternal infection as it takes this long for virus to get into the amniotic fluid. Whilst this can occur before 21 weeks gestation a negative test at this time does not exclude infection and it is therefore often better to wait until 21 weeks to do the test or repeat a negative test at 21 weeks.
 
With primary infection the risk of amniocentesis is much lower that the risk of having a child with congenital CMV. If CMV is reactivated in pregnancy then it is important to remember that the complication rate, including the risk of spontaneous foetal loss, due to amniocentesis is 0.1%, so not much lower than the risk of congenital CMV from reactivation itself and this can make decision making difficult.
 
Once the baby has been born congenital CMV is usually diagnosed by testing a urine sample for CMV DNA by PCR. If the baby is <3 weeks old then any CMV in urine confirms the diagnosis. From 3 weeks to 1 year CMV in urine is still likely to be congenital but post-natal infection cannot be ruled out, and after 1 year it is impossible to say. If a baby presents after 3 weeks it is usual practice to get parental consent to retrieve the newborn screening Guthrie card from storage (dried blood spot taken shortly after birth to screen for diseases such as cystic fibrosis, hypothyroidism, phenylketonuria, etc.) and test this for CMV DNA by PCR. A negative Guthrie card doesn’t rule out the diagnosis as the baby may not be viraemic (virus in blood) but a positive test is diagnostic for congenital CMV.
 
How is congenital CMV treated?
The treatment of congenital Cytomegalovirus infection is controversial and as of yet there is no clear evidence of the best way to manage these babies. The difficulty is finding a balance between preventing harm by treating the virus and causing harm with the treatment in asymptomatic babies even when they have a positive result.

​Long-term follow up of children with congenital CMV
All babies with congenital CMV, irrespective of whether they are symptomatic or not, should be followed up by an experienced Paediatrician. Hearing tests should be performed every 6 months until 3 years of age and then annually until 18 years of age. Eye assessments should be performed yearly or more frequently if abnormalities are detected. Regular dental check-ups are required to detect abnormal tooth development and developmental and neurological function should be monitored frequently.
 
So a decision was made to not start treatment and to follow-up our asymptomatic baby. Hearing and eye assessments were arranged and the plan was to see the baby in clinic a couple of weeks after discharge to make sure the baby remained well.
 
Many in the NNU MDT looked a little stunned having not expected the possibility of such a devastating diagnosis; we hope our baby continues to be one of the normal asymptomatic positive test babies…

The Biomedical Scientist walked hesitantly into the duty Microbiologists office.
 
“We have a mould growing in a blood culture” they said.
 
“You mean a yeast?” asked the Microbiologist.
 
“Nope, definitely a mould” replied the BMS.
 
“A contaminant maybe?” asked the Microbiologist again, now starting to hope this was the case.
 
“Nope, definitely not a contaminant” replied the BMS.
 
“Please tell me this was handled in Cat 3?” asked the Microbiologist again, starting to sound worried and thinking he should maybe put the Health and Safety Executive (HSE) telephone number into his phone!
 
“Nope, not in Cat 3” replied the BMS looking crest fallen, “but it should have been… I think it’s Talaromyces marneffei”
 
The Microbiologist just stared at them lost for words… why did it always happen when he was on duty?!
 
What is Talaromyces marneffei?
T. marneffei is a dimorphic fungus; it has two types of growth depending on the temperature (a bit like cheese! Cheese is a solid block when in the fridge but when sliced and put on toast under a grill it’s all gooey!!!) It used to be called Penicillium marneffei, but like many other microorganisms it has undergone a recent name change just to keep us on our toes.

On his way to review a ward patient the Microbiologist was stopped by one of the Consultant Physicians and asked about a different patient. These “corridor consultations” are fairly frequent in medicine and often lead to significant decisions about patient care, it’s important to document them though; remember, “if it isn’t written down then you didn’t do it”.
 
“I have a patient who I have been seeing in clinic who I think might have tuberculosis, but the sputum and bronchoalveolar lavage cultures are negative. Is there anything else that can present in the same way that I might be missing?” the Physician asked.
 
“Why do you think they have TB?” asked the Microbiologist, thinking is this related to those pesky Tabby Cats!?

The Microbiologist was slowly meandering through the daily authorisation, trying to stay awake and not authorise something important without seeing it first… honestly we do really pay attention but it can be a little dull authorising out more than a hundred urine results a day!
 
Suddenly something caught their eye. A wound swab was growing Candida auris. The Microbiologist sat up straight in his chair (I am notorious for slouching at the duty desk!) and picked up the phone to find out more.

It was a hot and dozy afternoon in the microbiology lab. The air-conditioning system was on the blink again and a nice large lunch of sausages, chips and beans had made the Microbiologist particularly sleepy. The telephone rang.

​​“My patient has plague!” screamed the excited junior doctor.

​I’ve had the dubious pleasure of dealing with various incidents and outbreaks over the years. They can be very stressful experiences for everyone concerned, but a clear methodical approach can go a long way to alleviating the levels of stress both in both you and your colleagues.
 
Imagine the scenario:
It’s 9am and the Senior Biomedical Scientist knocks on your door “ummm the laboratory has inadvertently processed a tissue sample containing Brucella melitensis on the open bench!”

“Can I notify a case of meningitis?” asked the sleepy sounding Junior Doctor.
 
“You notify Public Health England, not Microbiology” explained the Microbiologist.
 
“Damn, I thought I asked for PHE, sorry” said the Doctor. “Oh well, I‘ll call them in a moment. Can I ask you about the patient as well?”
 
“Sure”
 
“The patient is an eighteen year old student back from University for the holidays. They have a severe headache, neck stiffness and photophobia. We are about to do a lumbar puncture. Is there anything additional we should look for?”
 
“Don’t forget the protein and glucose, but have you thought of mumps? Has the patient been vaccinated?”
 
“Errrr….sorry I don’t know”
​

The Neurologist came to chat to the Microbiologist about a complex and puzzling patient. The patient had presented with back pain and acute retention of urine; she was also shown to have some weakness in her legs as well as brisk knee reflexes. The Neurologists had been convinced that she had some form of disc prolapse or some other lesion pressing on her spinal cord and so had done a scan of her back but this was completely normal.

​The Microbiologist asked where the patient had been born and after ringing the ward to find out the Neurologist reported that the patient had actually been born and spent her childhood in the Caribbean.

Five years ago The Daily Mail newspaper ran an article titled “Could you catch TB from YOUR tabby?” and of course as a Microbiologist and an owner of 5 cats, I had to blog on that!  However recently this subject has impacted my clinical work.

It was another dull and dreary afternoon giving advice when an excited Dermatologist phoned about a patient with funny skin lumps. (Microbiologists get excited about bugs, Dermatologists get excited about rashes, so lumps and bumps together… what can I say…we were very excited!!)
​
Their patient was a keen gardener who had been clearing a large number of blackthorn trees (good for making sloe gin) and despite wearing thick gloves had managed to get pricked and scratched all the way up their arms. At the site of one of those puncture wounds they had developed a small red lump which had eventually turned into a small ulcer. The ulcer hadn’t got much better and over the next few weeks the patient had noticed a number of other lumps appearing up their arm and then hard swellings in their armpit.